The present invention generally relates to a Visible Light Communication (VLC) system. More particularly, the present invention relates to a method and apparatus for transmitting status information about a Mobile Node (MN) in a Wireless Local Area Network (WLAN) system using VLC.
The Korean Agency for Technology and Standards (KATS) announced that traditional lighting would be replaced by Light Emitting Diode (LED) lighting by 2015. Due to their high luminous efficiency and low price, LEDs are gaining popularity in general illumination applications that had been dominated by fluorescence and incandescence. In addition LEDs are continually being used in special illumination applications such as portable devices, cars, displays, traffic signals, and advertising boards. White LEDs especially outperform incandescence in luminous efficiency and some white LED products outperform fluorescence light. Also, Radio Frequency (RF) exhaustion, probable incompatibility between wireless communication technologies, increasing communication security requirements, and the advent of an ultra high-speed ubiquitous communication environment of 4th Generation (4G) wireless technology are driving forces behind the recent increasing interest in visible light wireless communication technology that is mutually complementary to RF technology. Therefore, many companies and research institutes are conducting studies on visible light wireless communications using visible light LEDs.
While traditional fluorescent or incandescent lighting will be replaced by LED lighting with good performance and long lifetime in households, offices, and public places, a LED light can also be used as a communication light source by modulating a current applied to the LED. That is, broadcasting and data transmission are enabled with the LED light without an additional light source. A terminal user or a laptop user can make WLAN data communication using a visible light wireless transceiver module under LED lighting.
Visible light wireless communications are different from other wireless RF communications mainly in that data transmission and reception is visible to the user. That is, the user can easily locate visible light transceiver modules and can confirm a communication path. Based on these features, the user can establish a communication path between a transmitter and a receiver, while visibly locating visible light transceiver modules.
In real VLC, light sources other than a transmitting terminal and a receiving terminal may exist and visible lights from the light sources may be received at a visible light receiver of an Access Point (AP). In this case, there is a possibility that a plurality of mobile nodes may attempt access simultaneously; thus causing a collision. The collision leads to access delay and resource consumption. In this situation, communications could start according to a call setup procedure involving an initial access procedure that minimizes collisions and reduces resource consumption, rather than communications just starting when a visible light signal is incident upon the Access Point. Also, when a mobile node attempts an initial access, it should not interfere with communication signals from other mobile nodes.